It ain't that easy
Any of the commenters above have young children? I have a 3-year-old and an 8-year-old. It's hardly as easy the comments above suggest. When I'm minding the young one, how am I supposed to constantly monitor her older brother? I can't cut off net access, his school requires much of his homework be done through websites or apps, including Google Docs.
I can't tell you how many hours I have spent fiddling with privacy and parental control settings and applications between a chromebook, a tablet and the Xbox One his maternal uncle (and thus my wife) insisted on. And he still constantly finds loopholes. For example, I've cut off his YouTube access on all the devices. So imagine my surprise when I get copied on his e-mail that he has comments on his new video. He was making videos of himself and his sister with the tablet and, thanks to Google's integration of everything, sharing them to YouTube via the camera app.
And, BTW, this isn't about porn that I can just filter away. It's about the complete jerks that populate every corner of the web, from commenters on newspaper websites to popular YouTube stars to how gamers talk to each other. Starting around age 5, kids eat that stuff up. They think it's cool and it clearly affects how they act.
Frankly I would welcome some regulation here. Not of internet content, but requiring that devices offer useful and usable parental controls. For example, the parental controls on standard chromebooks are very limited. Such as you can either allow all apps or none. So if I want him to do school work on a chromebook, I have to allow alll. What is most annoying about this is that the chromebooks that google sells to schools can be tightly configured even down to per app time limits. Why can't they make that software available to parents? And why can't I easily configure an XBox to do something like only play games, allow anyone to play anything E10 and below, while disallowing chat and purchases? And Google needs kids' accounts - ones that let parents whitelist allowable activities. They let me do this with my staff at work so I know they have the capability.